1. Field of the Invention
This invention relates to a method of manufacturing an ink jet head to be used in an ink jet printer or the like, and more particularly to a method of manufacturing an ink jet head which is composed of a head substrate having ink passageways and Ink ejection openings, and a nozzle plate attached to the head substrate with an adhesive agent.
2. Description of the Related Art
Generally, in manufacturlng an ink jet head, a head substrate having a plurality of ink ejection openings arranged in rows is used.
FIG, 3 of the accompanying drawlngs illustrates a conventional method for manufacturing such an ink jet head.
As shown in FIG. 3, a plurality of ink ejection openings (hereinafter called "openings") 12 are formed in rows in a head substrate 10. Then a nozzle plate 14 is attached to the opening-side surface 10a of the head substrate 10 by means of an adhesive sheet 16. The adhesive sheet 16 is composed of a polyimide film as a reinforcement and a pair of adhesive layers attached to opposite surfaces of the polylmide film. The reinforcement has a thickness of about 25 .mu.m, and each of the adhesive layers has a thickness of about 10 .mu.m.
The resulting adhesive sheet 16 is sandwiched between the head substrate 10 and the nozzle plate 14, and the head substrate 10 and the nozzle plate 14 are then fixedly attached to one another by heatsetting the adhesive sheet 16.
Given that the nozzle plate 14 is fixedly attached to the head substrate 10, it is possible to jet out ink from fine ink jet nozzles (hereinafter called "nozzles") 18 precisely and accurately formed in the nozzle plate 14. If the nozzle plate 14 is formed of a stainless steel sheet or the like, it is possible to improve the rigidness of the whole ink jet head.
However, in the conventional method, since the head substrate 10 and the nozzle plate 14 are attached to one another by heatsetting the adhesive sheet 16 sandwiched therebetween, it is also necessary to form small holes 20 in the adhesive sheet 16 so as to communicate with the openings 12. The small holes 20 have to be formed at very fine spaces with precision, which would be extremely difficult to achieve.
As a consequence, mispositioning of the small holes 20 in the adhesive sheet 16 would occur so that part of the adhesive layer of the adhesive sheet 16 would flow into the openings 12 of the head substrate 10 and become hard there while the head substrate 10 and the nozzle plate 14 are being joined together using the adhesive sheet 16 in which the small holes 20 have been displaced. This would impair the proper ink jetting action.
There is a limit in reducing the diameter of the individual small holes of the adhesive sheet 16. Therefore, if the nozzles and openings 12 are formed in such a high density that the distance between the openings 12 is smaller than the diameter of the small hole 20, the individual small holes would overlap one another to form combined elongate holes so that the independency between the individual openings and hence the independency between the individual nozzles cannot be achieved, thus unabling high-quality printing.